Under Impedance Protection For Generators And Transformers Zgvpdis; Identification; Application - ABB RELION 670 Series Applications Manual

1MRK 504 152-UEN B
IN> : The setting of the residual current level (neutral current) which is used by the evaluation
logic to verify that a cross-country fault exists. The setting can typically be 20% of base
current (
earthing. Note that the systems are high impedance earthed which means that the earth-fault
currents at earth-faults are limited and the occurring IN above this level shows that there
exists a two-phase fault on this line and a parallel line where the IN is the fault current level in
the faulty phase. A high sensitivity need not to be achieved as the two-phase fault level
normally is well above base current.
tIN : The time delay for detecting that the fault is cross-country. Normal time setting is 0.1 -
0.15 s.
tUN : The time delay for a secure UN detecting that the fault is an earth-fault or double earth-
fault with residual voltage. Normal time setting is 0.1 - 0.15 s.
tOffUN : The UN voltage has a reset drop-off to ensure correct function without timing
problems. Normal time setting is 0.1 s
7.19 Under impedance protection for generators and
transformers ZGVPDIS
7.19.1

Identification

Function description
Under impedance function for
generators and transformers
7.19.2

Application

Under impedance protection for generator is generally used as back up protection for faults
on generator, transformer and transmission lines. Zone 1 can be used to provide high speed
protection for phase faults in the generator, bus ducts or cables and part of the generator
transformer. Zone 2 can be used to cover generator transformer and power plant's substation
bus-bar. Zone 3 can be used to cover power system faults.
The under impedance protection is provided with undervoltage detection feature in order to
provide the seal-in for the impedance based trip. Additionally, it is provided with load
encroachment feature in order to avoid tripping of the protection during heavy load
conditions. The load encroachment functionality is based on the positive sequence
components of voltage and current.
Characteristics of backup impedance protection
Characteristics of zone 1, zone 2 and zone 3 are shown in figure 236. All zones have offset mho
characteristics with adjustable reach in forward and reverse direction. The characteristic angle
for all three zones is common and adjustable. A load encroachment blinder feature is provided
for zone 2 and zone 3.
Application manual
IBase ) but the setting shall be above the maximum current generated by the system
IEC 61850 IEC 60617
identification identification
ZGVPDIS
S00346 V1 EN-US
Section 7
Impedance protection
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ANSI/
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GUID-ACC76B44-C071-4034-AB9D-880A77E12E66 v2
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